No heat in winter: a safe furnace checklist before requesting emergency repair
What to check when the heat stops, what information helps an HVAC technician and when carbon-monoxide safety takes priority.
Updated September 28, 2026Basic checks before the service request
A no-heat call can sometimes begin with a simple control or power issue. Without disassembling equipment, check the thermostat setting, the normal furnace service switch and whether the dedicated breaker has tripped.
- Thermostat is set to heat and above room temperature
- Furnace service switch has not been turned off accidentally
- Breaker has not tripped
- Record any visible error code before changing settings
Carbon monoxide changes the situation
Carbon monoxide is invisible and odourless. Ontario advises occupants to leave the home immediately and call emergency services from outside if a CO alarm sounds, especially if anyone has symptoms such as headache, nausea, dizziness or confusion.
Give the technician useful triage details
A qualified request should include the heating-system type if known, whether there is no heat or reduced heat, thermostat behaviour, error codes and any unusual sound or smell.